Clinical Chemistry II Practice Test

Screening with serology is done first because antibody testing is noninvasive, sensitive, and helps decide whether invasive confirmation is needed. The most useful initial test is a tissue transglutaminase IgA (tTG-IgA) assay, ideally with a check of total IgA to catch any IgA deficiency that could mask a positive result. A positive serology result strongly indicates celiac disease and leads to confirmation by an intestinal biopsy obtained during upper endoscopy, which shows the characteristic villous atrophy and crypt changes. If IgA deficiency is present, IgG-based tests (such as tTG-IgG or DGP-IgG) are used instead. Gluten challenge is not the first step; it’s reserved for specific scenarios where the diagnosis remains uncertain after initial testing or when a patient has been on a gluten-free diet.